Failure behavior of nuclear-grade FeCrAl cladding under simulated pellet-cladding mechanical interaction conditions

The performance of accident-tolerant nuclear cladding candidates must be assessed under simulated reactivity-initiated accident (RIA) conditions to evaluate the safety of nuclear fuel rods. During RIA, a rapid temperature increase causes the fuel thermal expansion. Eventually, the pellet expansion fills the pellet-clad gap and causes pellet-clad mechanical interaction (PCMI). Under PCMI, the pellet expansion imposes mechanical strain on the cladding, which may lead to cladding failure. The simulated PCMI test involves a one-inch specimen that is rapidly pressurized with a hydraulic system, which causes the specimen to burst under the biaxial stress state that can be related to PCMI loading conditions. In this study, we investigated the effect of pressurization-rate on the failure behavior of the nuclear-grade FeCrAl cladding candidate at 275°C. Deformation and rupture of the specimens were tracked with a telecentric lens and high-speed camera system. Outer surface strains were calculated using digital image correlation (DIC) on speckle patterns painted on the specimen outer surface. The failure strain was DIC-calculated in the range of 2-4% at 275°C, and the failure behavior is understood by the change in burst characteristics of the tubes.